The invention relates generally to antennas and, more particularly, to dual band array antennas.
In applications where multiple antennas are needed but space is very limited, an antenna system having two antennas operating at different frequencies while sharing a common antenna aperture would be desirable. Where each antenna sharing the common aperture possesses a separate feed system and beam steering control, then multiple independent tasks can be performed by the single antenna aperture. The beams for each antenna can be steered independently and simultaneously.
Problems existing in prior art techniques for sharing an antenna aperture between two antennas include the generation of grating lobes, poor impedance matching in the lower frequency elements due to the presence of the higher frequency elements in the common aperture, and the mutual coupling of power into the other antenna elements. Applications requiring a wide scan angle with low side lobe levels and with no grating lobe formation have also posed design problems and have not been satisfactorily overcome.